Originally Posted by WearyTraveler
While we’re sitting here watching the world go by...
Yesterday, I posed (and you folks answered perfectly) the question about the inverter. So - we drove for about 8 hours with the inverter on and the fridge powered. We were smiling as we cruised down the highway...
When we stopped last night and I checked the batteries before firing up the gen, the gauge (lights, actually) showed that the batteries were only half charged.
I was assuming that the V’s alternator would charge the house batteries on the fly.
Did we screw up by doing this? Or doesn’t the alternator keep up with battery power depletion?
Your 175 amp alternator has about 1,700 watts @ 2,400 engine RPM (500 watts @ idle rpm) usable output, so all is fine to run the fridge IF you are not using other things in the coach. The problem is dash A/C draws about 500 watts, headlights 120 watts, TV 65 watts, fridge 350 watts unless your door heaters are on then 660 watts. If the fridge in defrost mode then 1400 watts. Your MSW inverter is about 60% efficient when powering electric motors, so 635 watts of alternator power to power the fridge through the alternator.
You are going to have to learn about battery management if you are going to dry camp. Flooded batteries start to loose some of their ability to accept a full charge the day they are filled with acid. The deeper you discharge them the more life you take out of them. The typical life of a flooded battery discharged to 50% 60 days a year is usually 2 years. They don't fail; they just don't recharge to anything like full capacity. Any flooded battery will age rapidity if left 24 hours or longer in a partially discharged state. A new battery discharged to near zero a couple times will likely never recover.
The best check of the house batteries is when there is no power charging the batteries (engine off, generator off and not on shore power). Turning the inverter on will show actual battery voltage - 12.8 volts fully charged; 12.2 volts 50% charged; 12.1 volts 25% charge and 11.9 volts 0% charged. More info @ <https://www.batterystuff.com/kb/articles/battery-articles/battery-basics.html>